There is a well recognized need to improve the therapy of childhood neuroblastoma. Our studies aim to characterize neuroblastoma cell surface antigens (CSA) by serologic and biochemical criteria and then to develop immunologic tests and immunotherapy utilizing them. To characterize CSA, we use cultured neuroblastoma cells and non-cultured tumors and tissues, monoclonal antibodies produced by lymphocyte hybridomas, rabbit and human antisera, the radioiodinated protein A assay for cell surface bound antibodies, and isoelectric focusing/polyacrylamide gel electrophoretic analysis of immunoprecipitated neuroblastoma cells or for fetal cells. Immunologic tests will include quantitation released (shed) CSA and determination of CSA phenotype. These tests may provide means of classifying tumors and of predicting and monitoring the response of neuroblastoma to therapy. Some CSA may serve as targets for immunologically specific cytotoxic or cytostatic reactions providing considerable therapeutic potential. Clinical studies of children with neuroblastoma and others will determine the incidence of antibody responses to CSA as an indicator of immunogenicity, and in vitro and in vivo model studies will determine the ability of antibodies to affect neuroblastoma cell survival and growth. Development of immunologic tests and immunotherapy should significantly contribute to our long-term aim of achieving optimal therapy for children with neuroblastoma.